Printout process and leuco bases of triphenyl methane dyes used therein



United States Patent O 3,140,949 PRINTOUT PROCESS AND LEUCO BASES F TRIPHENYL METHANE DYES USED THEREIN Robert H. Sprague, Chagrin Falls, and John A. Stewart, Parma, Ohio, assignors to Horizons Incorporated, a corporation of New Jersey No Drawing. Filed June 7, 1962, Ser. No. 200,664 8 Claims. (Cl. 96--48) This invention relates to photosensitive compositions based on leuco Crystal Violet or leuco Opal Blue or similar leuco bases of triphenyl methane dyes. More particularly, it relates to the use of organic acids and acid anhydrides to enhance the visible light photosensitivity of photosensitive compositions based on leuco bases of triphenyl methane dyes.

The constituents comprising the visible light sensitive compositions of the present invention include the following classes of materials: (a) leuco base of at least one triphenylmethane dye; (b) an activator which when mixed with the leuco base, enhances, the visible light sensitivity of the leuco base; and (c) a binder, support or carrier on which or in which the remaining constituents are dispersed or supported. Other ingredients, e.g., those added for specific purposes, may be added to the compositions constituting the present invention provided they do not adversely aifect the cooperation between the photosensitizer and the leuco base. For example, a plasticizer added to the carrier would constitute one such addition.

(1) THE LEUCO BASE OR PHOTOSENSITIVE MATERIAL The sensitive materials utilized in the present photosystem comprise the leuco bases of triphenylmethane dyes, such as leuco Crystal Violet. The leuco bases of other triphenylmethane dyes may be used including the leuco bases represented by the general formula R H R wherein R R R and R are each selected from the group consisting of H, alkyl, aralkyl, and aryl and they may be the same or different and R represents a monovalent radical selected from the group consisting of H and wherein R and R have the same meaning as above.

Suitable leuco bases include leuco Opal Blue, leuco Crystal Violet, leuco Malachite Green, leuco Brilliant Green, leuco Victoria Blue, leuco Methyl Violet, and similar leuco bases.

(2) THE ACTIVATOR OR SENSITIZER Organic acids and acid anhydrides of the types exemplified in the examples below are illustrative of the diversity of activators which are useful in the present invention. Both monocarboxylic and polycarboxylic acids and their anhydrides may be used.

The acids may be represented by the general formula RCOOH wherein R represents both straight and branched chain alkyl, alkylene, aralkyl or otherwise substituted acyclic monovalent radical, or it represents aryl or substituted aryl monovalent radicals. the acids may also be utilized.

(3) THE CARRIER Both the leuco base and the activator are preferably placed in solution to facilitate mixing them with one another and for the purpose of applying them to a chemically inert support such as paper, plastic or other material in order that the composition may be photographically exposed as a thin layer. Instead of, or in addition to a support of the type indicated, it is often preferable to include a film-forming plastic in the solution of leuco base and activator, particularly when a non-absorbent base such as glass or unsubbed plastic is to serve as the support for the photosensitive composition. It will be understood that such a binder may be omitted when the solution of leuco base and activator is applied to an absorbent support such as filter paper. Both the solid carrier and the film-forming plastic are selected from materials which are inert chemically to the remaining constituents of the photosensitive composition.

Polystyrene is the film-forming synthetic polymer preferred in the present system, but it will be appreciated that other polymers of vinyl or vinylidene monomers and film-forming cellulose derivatives may be used in place of the polystyrene.

(4) PROPORTIONS Anhydrides of The addition of small amounts of one or more activators of the types described above to leuco bases of triphenyl methane dyes imparts an increased sensitivity to the leuco base, as is indicated by the increase in density of the visible image obtained directly and without any further processing, when such compositions are exposed to visible lightas compared with the .density of image obtained by exposure of the leuco base to the same visible light source, in the absence of any organic acid or acid anhydride of the type described.

The relative proportions of activator to leuco base depend to some extent upon the specific materials. In general approximately 8 parts of acid or anhydride to 1 part of the leuco base appeared to produce optimum activation (image intensification). Between about 4 and 24 parts by weight of activator per 1 part by weight of leuco base appears to represent a desirable working range for exposure intervals between 2 and 30 seconds, to radiation in the visible.

The following examples are illustrative of the practice of the prment invention.

Example 1 A solution of leuco Opal Blue was prepared by dissolving 0.5 g. in 5 cc. of acetone. Ten cc. of a 10% solution of polystyrene in benzene was added to the leuco Opal Blue solution and then 0.3 gram of 2,4-dichlorophenoxyacetic acid or other acid noted below was dissolved injthe resulting composition. V j

The resulting solution was applied to unsubbed. Mylar (terephthalate polyester) at a coating thickness of 0.0015 inch, wet coating thickness, and then air dried prior to exposure.

After the film was dried, it was exposed to one No. 2 reflector photofiood lamp at 12 inches distance for 5 minutes, through a step wedge with the several Wratten filters indicated below. A portion of the sheet was not exposed at all (see column labeled base plus fog) and a portion was exposed without any filter (see column labeled clear).

As a result of this exposure and after heating to C. to fix the film, the following densities were obtained,

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measured with an Eastman Model-l color densitometer through a red filter:

Table I.DENSI'IIES RESULTING FROM USE OF ACID AOTIVATORS WITH LEUCO OPAL BLUE [Coatings of Mylar film. Densities read on Eastman Model-1 color deusitometer through the red filter] Wratten Filters 2B Blue 12-Yellow Clear 58-Green 25A-Rcd Base Activators plus Fog 21st 21st 21st 21st 21st 21st No.01 Step, No.01 Step, No. of Step, No. of Step, No. of Step, No.01 Stop, Steps Gross Steps Gross Steps Gross Steps Gross Steps Gross Steps Gross Den. Den. Den. Den. Den. Den.

2,4-Dichlorophenxy Acetic Acid (2,4-D) 11 1. e5 0 .21 12 1.63 13 1.67 5 .44 1.40 .18 Bromoacetic Acid 12 1. 70 1 .20 12 1. 75 13 1.83 5 .51 10 1.55 .15 2,4,5-Trichlorophe 9 1.60 0 .20 0 1. 50 10 1. 64 3 .29 7 1. .20 o-Ghlorophenoxyacetic Acid 8 77 O 12 6 .65 7 .58 0 14 0 13 11 Tribromoacetie Acid (0.25 g.) 5 .74 1 .45 7 .83 10 .94 2 .57 5 72 .34 Ohloroacetic Acid 1 (0.5 g.) 10 .88 0 12 11 .94 12 1. (l6 4 30 9 80 .09

1 Heat 30 sec. at 150 C.

When bromoacetic acid and the other acids indicated, TABLE III were each substituted for the 2,4-D, the results indicated above were obtained. Reflector Flood Lam No.2

Similar results were obtained when leuco Opal Blue fg igig g g i was activated with acid anhydrides as may be seen from D s y the following examples. Wmttcn Filter Base Base Gross plus Net Gross plus Net Example 2 Fog Fog Leuco Opal Blue (125 mg.) and phthalic anhydride 153 40 1.44 1.01 43 (125 m were dissolved in 4 cc. of acetone, and the kg 8; g; {8% solution was poured on filter paper and dried in the dark. 1.67 1.07 231 The sensitizedpaper was then exposed to the light of a {22 i8; 34 04 General Electric Photofiood No. 2 lamp for 90 seconds at a distance of 12 inches under a silver step tablet which was Example 4 partly covered with strips of Wratten filters-2B (ultraviolet absorbing), Blue No. 47B, Yellow No. 12, Green No. 58, Red No. 25A. The densities produced on a piece of paper by! this exposure were read on an Eastman Model-1 colored densitometer, using the red filter. Results are tabulated in Table II.

A similar piece of sensitized paper was exposed under the same step table-filter combination to the light of a General Electric sunlamp for 90 seconds. The densities resulting from this exposure are also given in Table II.

The results show that the sensitivity is almost entirely to the visible light, chiefly to red and green.

Coatings were made in the same fashion as in Example 1, using leuco Crystal Violet in place of leuco Opal Blue. Exposures were made similarly, and the resulting densities are recorded in Table HI.

Coating mixtures were prepared by mixing four parts by weight of a 6% solution of leuco Crystal Violet in toluene with two parts by weight of the activator when the activating acid or acid anhydride was a liquid or with four parts by weight of a 20% solution of the activator, in toluene, when the activating acid or acid anhydride was a solid.

Baryta-coated paper which had previously been subbed with a Butvar lacquer to prevent penetration of the sensitive coating into the base paper was used as support. Coating thickness was .003-inch wet film, applied by drawndown technique using a Bird applicator. After drying, the materials were exposed at a distance of 12 inches to the light from a General Electric sunlamp for 10 seconds, followed by 30 seconds heat treatment under a GE infrared heat lamp at 4 inches distance.

The density of the resulting image was read under the green filter on an Eastman Kodak No. 1 color densitometer. Results of tests are listed in Table IV; comparison being made in each case with a leuco Crystal Violet coating containing the indicated activator and simultaneously exposed with a coating containing leuco Crystal V1olet without added act1vator.

LOV Plus LCV Alone Acid 1. a-Bromo-n-butyric acid 0. 52 0. 29 2. Stearic acid 0.39 0.20 3. Succinic acid. O. 50 0. 39 4. Adipic acid 0. 26 0.20 5. Itaconic aci i 0.38 0.19 6. Benzoic acid 0. 96 0.15 7. 2,4-diehlorophenoxyacctic acid 1.69 0.28 8. Anthranilie acid 0.98 0.17 9. p-Ohlorobenzoic acid O. 43 0.20 10. Furoic acid 1. 24 0. 28 11. Citric acid 1 0.40 0.20 12. m-Nitrohenzoic acid 1. 56 0.38 13. o-Phthalic acid 1.14 0. 14

Example 5 Coatings were made in the same fashion as in Example 4, using the following anhydrides, exposing to the sunlamp as before, and gave the following densities:

LVC Plus Leuco Anhydriclc Anhydride Crystal Violet Alone Phthalic anhydride Suceinie anhydride" Maleic anhydride. Acetic anhydride. Benzoic anhydride The photosensitive material produced by this invention may be used to prepare photographic prints by either contact or projection printing from a negative, such as microfilm, using visible light sources. When coated on a transparent base the material may be used for preparation of a positive transparency from which contact prints may be made on diazo paper. The latter procedure is especially useful in the field of engineering drawing retrieval from microfilm, where a positive diazo copy is desired.

Having now described the invention in accordance with the patent statutes, it is not intended that the invention be limited except as required by the appended claims.

We claim:

1. A photographic material comprising a composition consisting essentially of a leuco base of a triphenyl methane dye represented by the general formula R5 wherein R R R and R are each selected from the group consisting of H, alkyl, aralkyl, and aryl and may be dilferent and R represents a monovalent radical selected from the group consisting of -H and wherein R and R have the same meaning as above, and a material increasing the visible light sensitivity of said leuco base, selected from the group consisting of carboxylic acids and carboxylic acid anhydrides there being between 4 and 24 parts by weight of said material for each part by Weight of said leuco base in said composition and said composition being supported by a carrier material which is chemically inert thereto.

2. The photographic material of claim 1 wherein the composition is dispersed in a film-forming plastic binder.

3. The photographic material of claim 1 wherein the composition is coated on a paper base.

4. The photographic material of claim 1 wherein the material increasing the visible light sensitivity of said leuco base is benzoic acid.

5. The photographic material of claim 1 wherein the material increasing the visible light sensitivity of said leuco base is a halogen substituted acetic acid.

6. The photographic material of claim 1 wherein the material increasing the visible light sensitivity of said leuco base is a halogen substituted phenoxyacetic acid.

7. A method of producing a visible image which comprises: preparing a member including a thin layer containing a mixture consisting essentially of a leuco base of a triphenyl methane dye represented by the general formula wherein R R R and R are each selected from the group consisting of H, alkyl, aralkyl, and aryl and may be difierent and R represents a monovalent radical selected from the group consisting of H and wherein R and R have the same meaning as above, and a material increasing the visible light sensitivity of said leuco base and selected from the group consisting of carboxylic acids and carboxylic acid anhydrides, there being between 4 and 24 parts by weight of said material for each part by weight of leuco base in said composition, exposing said layer to a pattern of visible light; thereby producing a visible image on the areas exposed to visible light and thereafter fixing the image.

8. The method of claim 7 wherein the exposure is through a photographic negative.

References Cited in the file of this patent UNITED STATES PATENTS 2,325,068 Chalkley June 27, 1943 2,366,179 Chalkley Jan. 2, 1945 2,441,561 Chalkley May 18, 1948 2,528,496 Chalkley Nov. 7, 1950 2,829,052 Chalkley Apr. 1, 1958 2,927,025 Ryskiewicz Mar. 1, 1960 OTHER REFERENCES Glafkides: Photographic Chemistry, Fountain Press, London, 1960, vol. 2, page 713. 

1. A PHOTOGRAPHIC MATERIAL COMPRISING A COMPOSITION CONSISTING ESSENTIALLY OF A LEUCO BASE OF A TRIPHENYL METHANE DYE REPRESENTED BY THE GENERAL FORMULA 